In an axial flow gas turbine, a plurality of blades or buckets are attached to each of the turbine rotor disks or wheels, often by means of a mated engagement between a dovetail or fir tree-shaped section at the base of the blade or bucket (referred to sometimes herein as an “attachment portion”) and a corresponding axially-extending slot formed in the rotor disk. While these arrangements provide excellent radial retention, additional means must be provided for retaining each blade or bucket against axial movement within its respective rotor disk slot. In addition, it is necessary to seal the turbine bucket/turbine wheel attachment interface on the downstream side of the disk. In this regard, cooling air is typically directed into clearance slots or root manifolds in the wheel, inboard of the individual bucket attachments from which it flows into internal cavities of the buckets. While the typical dovetail or fir tree attachment portion of each blade or bucket fits snugly into the corresponding slot in the rotor disk, manufacturing tolerances and differences from blade-to-blade and wheel-to-wheel result in leakage at the ends of the root manifolds between the buckets and the disks. As a result, end cover plates are normally installed to reduce such leakage. It is desirable that such end cover plates be of relatively simple and cost-effective design.
There remains a need for more efficient and more effective means for attaching the seal plates to the turbine rotor wheels or disks not only to seal against leakage but also to provide a locking function such that the buckets cannot move axially within their respective disk slots.